Seven US sailors have been missing after a U.S. Navy destroyer collided with a merchant ship off the coast of Japan.

The commanding officer of the ship, Cmdr. Bryce Benson, is among the injured according to a statement by the U.S. Navy.

USS Fitzgerald suffered damage to its starboard side above and below the waterline in the incident. Benson was one of four injured sailors who needed to be flown to a naval hospital in Yokosuka, Japan, reports the CNN.

U.S. Navy Chief of Naval Operations Adm. John Richardson said four sailors were medevaced.

Other injured sailors are being assessed, the Navy said.

The two ships collided in the Pacific Ocean about 56 nautical miles off the coast of Yokosuka. The damage to the Fitzgerald resulted in some flooding.

The vessel was taking on water after the incident, but the crew was working to stabilise the ship by pumping water out of the hold.

The Japanese coast guard said four of its vessels and one helicopter were assisting the U.S. Naval destroyer with damage assessment and searching the area around the ship, working on the possibility that some of the missing may have fallen into the ocean.

The merchant vessel involved in the collision is the ACX Crystal based in the Philippines.

The USS Fitzgerald requested the assistance of the Japanese coast guard after the collision occurred at approximately 2.30 a.m. Saturday